Yesterday I used the Laptop pretty much all day on battery mode. When I came home, the thing was plugged in and connected to an external monitor. I adjusted the screen and x crashed telling me to log out and back in. Since then the internal Touchpad quit its job while the Trackpoint works just fine. I reinstalled the Synaptic driver and Cinnamon, but it still doesn't function.

Maybe this problem is Cinnamon or Gnome related, I don't know.

UPDATE: A fresh system install, checking BIOS settings and updating to the latest version did not do the trick.

The fact you've done a fresh install and no go has thrown me a bit - my solution may be useless but worth a try. I'm running Cinnamon on standard Mint 12 on a lenovo T60 laptop. Lost my touchpad while fooling around with settings - don't know what happened really. Trackpad still working. After trying a number of things, I found a Cinnamon applet called Touchpad indicator here - http://cinnamon-spices.linuxmint.com/applets/view/44. Instal by downloading and unzipping to /home/.local/share/cinnamon/applets.Add to panel and open - set enable touchpad to on.Good luck

Thanks for your suggestion. Actually I didn't get to try it because I added the PPA, installed some additional applets and tried them. Some don't work and others just completely crash Cinnamon. Who knows which setting or file it was in the end, but deleting all Cinnamon folders in /home did the trick. The touchpad works for now.

I've been having this exact problem on and off for a while now. Seemingly random on an Inspiron 1521. I figured it was something else happening because the mouse would just stop working so id restart X and it would work again. Recently that seemed to not work and then i got the idea to try plugging a usb mouse in which worked. I searched for a solution and found this one.

I've used the modprobe psmouse and it solved the problem. The module was not loaded so the rmmod wasnt needed in my case.